Various types of catheters and associated methods for the delivery of medical devices/instruments to target sites within a patient's body are known in the art. A properly positioned catheter can provide a convenient conduit for an operator/clinician to pass an elongate medical device, such as a medical electrical lead, into the body in order to deliver a site specific therapy from the device. However, the task of preventing excessive leakage/backflow of bodily fluids, for example, blood, and/or other procedure-related fluids out from a positioned catheter can, at times, somewhat complicate catheter delivery procedures.
With reference to FIG. 1, a portion of a catheter delivery system, which is known in the art, is shown. FIG. 1 illustrates the system including a catheter 800, a sealing assembly 820, a syringe 810, a relatively smaller diameter guide wire 200, a relatively larger diameter guide wire 200′ and an insertion accessory tool 822, for example, to assist in inserting devices/instruments, such as guide wires 200/200′, a medical electrical lead and a sub-selecting catheter, into catheter 800. An example of the illustrated catheter 800 is the Attain Command® Catheter, available from Medtronic, Inc., and examples of the illustrated guide wires 200/200′ can be any of the many suitable guide wires known to those skilled in the art; an example of the sealing assembly 820 and associated insertion tool 822 is the SafeSheath® Sealing Adapter and associated Transvalvular Insertion Tool, available from Pressure Products. According to FIG. 1, sealing assembly 820 is connected to catheter 800 by inserting a distal end 823 of assembly 820 into a hub 811 of catheter 800, and, once connected, a valve/seal member (for example, like that described in U.S. Pat. Nos. 5,125,904, 5,312,355 and 5,409,463), which is located within a body 825 of assembly 820, in proximity to a proximal end 824 thereof, both seals off a lumen of catheter 800 and provides a passageway into the lumen. This passageway, into the lumen of catheter 800, is intended to allow passage of a medical device, for example, a medical electrical lead, therethrough, so that the operator may deliver the device, through the lumen of catheter 800, to a target site, within a body of a patient. The valve/seal member of assembly 820 is designed to seal around the device as it passes therethrough and thereby prevent an excessive volume of bodily fluids from leaking out from proximal end 824, and the design thereof is such that tool 822 is typically required to provide passage therethrough for the device.
The valve/seal member may further seal about a dilator device (not shown), which facilitates introduction of catheter 800 into the patient's venous system via a venous access site. Larger diameter guide wire 200′, for example, having a 0.035 inch diameter, may be used to gain initial access and the dilator, having a uniform inner diameter provides a passageway through the valve/seal member as the operator introduces catheter 800 over guide wire 200′, in order to position distal end 89 of catheter within the venous system, according to methods known in the art, prior to delivering the medical device through the lumen. Smaller diameter guide wire 200, for example, having a diameter of approximately 0.014 inch, may be used to facilitate the delivery of the device. Upon removal of the dilator and the larger diameter guide wire 200′, smaller diameter guide wire 200 may be loaded into the lumen of catheter 800 from proximal end 824 of sealing assembly 820, wherein insertion tool 822 may be necessary to facilitate insertion of a distal tip 209 of guide wire 200, which is typically somewhat floppy and deformable, through the valve/seal member of assembly 820. Tool 822 is a disposable tubular member that is easily peeled away from around loaded guide wire 200, by pulling apart ends 802. Alternately, if a guide wire is not employed, tool 822 may assist in inserting a medical device, such as an electrical lead, into the lumen of catheter 800, after which, tool 822 may be peeled away from around the inserted device.
FIG. 1 further illustrates sealing assembly 820 including a side tubing port 826 extending to a stopcock 827, which is coupled to syringe 810; tubing port 826 provides a passageway for the injection of a fluid from syringe 810 into the lumen of catheter 800, downstream or distal of the valve/seal member of valve assembly 820. The fluid may be a saline flush or a radiopaque contrast agent that is useful for visualizing anatomy, for example, a venous anatomy on fluoroscopy, which is downstream of distal end 89 of catheter 800, and thereby facilitate the positioning of distal end 89, guidewire 200 and/or the medical device at, or in proximity to a target site. Thus, the valve/seal member of assembly 820 must also prevent backflow of the fluid injected from syringe 810 around both guide wire 200 and the medical device, which are either together or individually inserted through the valve/seal member.
Once the medical device is delivered to the target site through catheter 800, if the medical device is to remain implanted within the body at the site, catheter 800 is removed out from the body and from around the medical device. FIG. 1 shows a dashed line extending along a length of sealing assembly 820 to represent a weakened section along which sealing assembly 820 may be split apart for removal from around the implanted medical device body. Splitting apart sealing assembly 820 is necessary when a proximal end of the implanted medical device will not fit through the valve/seal member of the assembly. Other sealing assemblies known in the art, for example, the Toughy-borst type, are configured to allow the operator to expand and contract the corresponding valve/seal member such that in the contracted state, the valve/seal member seals around a device inserted therethrough, and in the expanded state the valve/seal member is sufficiently opened so that a larger proximal end of the device will fit through the valve/seal member. Having the ability to alternately expand and contract the valve/seal member can alternately facilitate the movement of devices and guide wires through the valve/seal member, when expanded, and provide better sealing, when contracted, but also requires additional manipulations from the operator, which can make the catheter delivery procedure a bit more tedious. Toughy-borst type sealing assemblies may also include a tubing port connected thereto, similar to that described above, so that fluid may be injected through catheter 800 downstream of the valve member thereof.
Although the above-described valve assemblies enable catheter delivery procedures, there is still a need for improved apparatus and methods that can prevent excessive leakage/backflow and facilitate simpler catheter delivery procedures.